The present invention relates to a method of production of frozen minced fish meat containing additives (referred to as "frozen surimi" hereinafter).
In a conventional method, frozen surimi is produced by washing minced fish meat obtained from raw fish meat, such as Walleye pollack, with fresh water two or more times. The minced fish meat is then washed with water containing a small amount of salts and, if necessary, the black skin is removed through a refiner. The fish meat is dehydrated through use of a filter press, screw press or the like, and sugars or sugar alcohols and polyphosphates and the like are added. The fish meat is then packed, frozen and held at -20.degree. to -30.degree. C.
According to the above method, the added sugars, sugar alcohols and phosphates denaturate the protein in frozen surimi upon freezing, so as to make it impossible to store frozen surimi for long periods of time.
However, when the minced fish meat is washed with water during production of the frozen ground surimi, especially in winter, the minced fish meat is liable to hydrate with an excess amount of water. This excess hydration causes the fish meat to swell and makes the dehydration difficult. In addition, a portion of the myofibrillar proteins in the fish meat dissolves in the water. In order to prevent such a phenomenon, a small amount of salts has been added to the wash water, but insufficient dehydration is thereby achieved. This results in a poor yield due to the removal of fish meat protein with water.
In order to solve the above problems, it was proposed to use a final wash water containing calcium salts and/or magnesium salts.
However, in such a method it is difficult to delicately control the dehydration of the washed minced fish meat. For example, the amount of water and the concentration of salts to be added to a given amount of dehydrated minced fish meat will vary according to the condition of the fish meat (which is changed according to the season), size of the fish, freshness and so on. Additionally, due to the fact that the solubility of the myofibrillar protein is reduced by the addition of calcium salts or magnesium salts, some kinds of fish meat give hard paste products which can not be regenerated. Therefore, in spite of the recognized dehydrating effect of calcium salts and magnesium salts, these salts have not been actually used because of these difficulties in use.
As a compromise method, it was proposed in Japanese patent application No. 7421-1985 and Japanese patent application No. 172379/1985 that sodium salts, such as NaCl or NaHCO.sub.3, be added with calcium salts and/or magnesium salts to the wash water to weaken the dehydrating action of the latter salts.
On the other hand, it was proposed that in order to improve the quality of the frozen surimi that surface active agents be added. For instance, there is proposed in Japanese Patent KOKAI No. 89061/1979 that the whiteness and brightness of frozen surimi is improved by the addition of monoglycerides to prevent freezing denaturation of the protein through freezing. Further, it is proposed in Japanese Patent KOKAI Nos. 9350/1978 and 133667/1978 that the elasticity and whiteness of frozen surimi is improved by the co-use of sugars and sugar alcohols with monoglycerides. However, it has been unexpectedly found that the water-solubility of the hard dehydrated minced meat obtained with calcium salts- or magnesium salts-containing water is increased by the addition of surface active agents and glycerides, so as to soften the minced meat. However, the prior art does not suggest that surface active agents or glycerides are effective for softening frozen surimi hardened by excess dehydration or the release of myofibrillar protein into water.